The disappearance of the helium-giant progenitor of the type Ib supernova iPTF13bvn and constraints on its companion

TL;DR

This study confirms the progenitor of supernova iPTF13bvn has disappeared, constrains its initial mass to 10-12 solar masses, and suggests the progenitor was a helium giant rather than a Wolf-Rayet star.

Contribution

It provides the first observational confirmation of the progenitor's disappearance and constrains its nature and mass, offering new insights into supernova progenitors.

Findings

Progenitor star has vanished after explosion.

Progenitor's initial mass is between 10 and 12 solar masses.

Progenitor was likely a helium giant, not a Wolf-Rayet star.

Abstract

We report and discuss post-explosion observations of supernova iPTF13bvn. We find that the brightness of the SN at +740 days is below the level of the pre-explosion source and thus confirm that the progenitor star has gone. We estimate that the late-time brightness is still dominated by the supernova, which constrains the magnitude and thus mass of a possible companion star to below approximately 10Msun. In turn this implies that the progenitor's initial mass is constrained to a narrow range of between 10 to 12Msun. The progenitor of iPTF13bvn would have been a helium giant rather than a Wolf-Rayet star. In addition, we suggest that sufficiently deep observations acquired in 2016 would now stand a chance to directly observe the companion star.